Single wire alternator

[jingo]

Looking through all the 3G posts...why don’t more folks just go for a single wire, internally regulated alternator? Why put a used or reman alt into the truck when I can get a brand new, modern one? Is it just about saving a few bucks and being thrifty?

Powermaster makes a small case, internally regulated 100 amp alternator that is an identical form fit to the original alternator. Single wire, bolts right in. Regulator, plug, harness issues gone.

Looking at the wiring schematic, the only appliance directly connected to the regulator looks like the horn, which is cross-connected in the regulator plug to the starter relay. There is also a wire from the ignition to power the regulator. I know my gauge won’t read anymore, but that’s ok, I have a set of aftermarket gauges under the dash installed by a PO anyway.

Seems like I could simply unplug and remove the external regulator, leave the plug intact/open, connect the new alternator directly to the battery, and it should work. But the schematic is pretty tricky to read, what else do I need to do to make this work?

Greatful for any advice or mods I need to make.

[Thipdar]

Looking through all the 3G posts...why don’t more folks just go for a single wire, internally regulated alternator? Why put a used or reman alt into the truck when I can get a brand new, modern one? Is it just about saving a few bucks and being thrifty?

Powermaster makes a small case, internally regulated 100 amp alternator that is an identical form fit to the original alternator. Single wire, bolts right in. Regulator, plug, harness issues gone.

Looking at the wiring schematic, the only appliance directly connected to the regulator looks like the horn, which is cross-connected in the regulator plug to the starter relay. There is also a wire from the ignition to power the regulator. I know my gauge won’t read anymore, but that’s ok, I have a set of aftermarket gauges under the dash installed by a PO anyway.

Seems like I could simply unplug and remove the external regulator, leave the plug intact/open, connect the new alternator directly to the battery, and it should work. But the schematic is pretty tricky to read, what else do I need to do to make this work?

Greatful for any advice or mods I need to make.

Could use a little background here... what year are you talking about?

Also, the wiring diagrams are subtly different for gauges vs. idiot lights, and one of those differences is reflected at the Voltage Regulator.
The Alternator light only needs to have voltage on or off, but the Alternator gauge needs to indicate a range of current from negative through positive. As a result, they need to check different parts of the electrical system in order to operate correctly.
I'm guessing here, but disconnecting the VR might mean (as you mentioned) that you lose the ability to indicate alternator function at the Instrument Cluster.
I don't see the horn circuit going through the VR at all.
This sort of modification seems like it will impact either the Fuse Link or the Resistance Wire from the Ignition Switch.

Pragmatically, undocumented changes to a vehicle can turn troubleshooting from a headache into a nightmare. I have enough trouble understanding how the theoretical (i.e. the Wiring Diagram) correlates to the physical reality in my truck without having to remember what doesn't apply because of re-engineering modifications.

If you do all of your own troubleshooting, go ahead and make all of the changes you're comfortable with.
If someone else does your troubleshooting for you, you run the risk of increasing their troubleshooting costs.

[sargentrs]

Here's a good explanation of how the remote voltage sensing works. Based on chebbie alternators of course. 1 wire alternator conversions are usually chebbie based.
http://www.madelectrical.com/electrical ... sing.shtml

Also other info on the conversions themselves.

[jingo]

I read the MAD link and several related articles on their site. I also traced every connection on the 1970 master wiring diagram relative to the regulator and alternator. I’m still not getting it.

The MAD argument is premised on “a very long wire” running from the alternator output to a “junction” of some sort, which they also conveniently offer for sale. But in our trucks there is no such “long” wire or junction per se.

The battery, alternator output, and regulator are all connected to the hot terminal of the starter relay. All of these components are nestled next to one and other, literally just inches apart. If there is some kind of ‘remote sensing’ feature or appliance elsewhere (other than the ammeter gauge in the cluster) I’m not seeing it.


It makes sense that all these components are clustered together, I don’t know why the system would be laid out any other way. The only mod I plan to make is to upgrade the three hot wires (battery, starter, and single wire from alternator) to from 6 gauge to 4 gauge to handle 100 amps.

Still looking for a reason 3G is talked up so much for our trucks, with rewiring, bracket shims, etc. Single wire alternators are frequently installed in 60s, 70s muscle cars, street rods, and race applications. What am I missing?

[Thipdar]

I also traced every connection on the 1970 master wiring diagram relative to the regulator and alternator. I’m still not getting it.

The 1970 Master Wiring Diagram is for those trucks that have Idiot Lights. If your truck has gauges, you'll need to look at a different schematic. Compare Wire #904 at the Voltage Regulators between the Master Wiring Diagrams for the 1970 F100/F250 and the 1970 F350 (which shows how things are done for gauges). Also, notice that the trucks with gauges only have a ground and two wires connecting at the Alternator - trucks with idiot lights have an additional wire at the Alternator.

Because the idiot light only has to be off ("0VDC") or on ("+12VDC"), it senses a different part of the charging circuit than does the ammeter that needs to measure a range from negative current through positive current.

[jingo]

Is there a 1970 master wiring schematic posted somewhere that shows the 4 gauge instrument panel?

[jingo]

Just got my alternator but it came with a serpentine pulley. There are several v-belt pulleys available, each with a different back spacing.

Does anyone know the correct back spacing on the stock 64 amp alternator?

Thanks

[Nitekruizer]

Unless the truck's wiring harness is toast, I can see just replacing the alternator, especially if the regulator is still good. The stock regulator will work with almost all of the factory style alternators. The VR regulates the field circuit of the alternator, which all are pretty close when it comes to amp draw. The alternator output current is not fed through the VR. You don't have a 60 or 100 amp current load going directly through the regulator. However, in some vehicles you do have the entire load going through the AMP Gauge and firewall bulkhead connector. This is where the MAD Conversion comes into play, but this mainly applies to Mopar vehicles of our truck's era. Mopar's could have 16 to 18 feet of wire running from their alternator, through the firewall connector to the dash gauge, back through the firewall connector, then through a Fuse Link and finally to the battery. I'm not convinced that 18 feet of #10 gauge wire couldn't carry the current of the original alternator, but rather all of the connections at the firewall and dash were the real issue, especially once the terminals at the firewall bulkhead connector became dirty or corroded. Ford didn't run the alternator output through the firewall to a dash gauge and then back to the engine compartment, so this shouldn't be a problem. Ford didn't even use bulkhead connectors in our trucks.

If you don't mind losing the dash gauge, you can run the 3G or similar "1 Wire" alternator. These alts have built in VRs, but most can use the idiot light if your truck has one. Upgrading the wire size between the alternator and battery side of the starter relay is a must and you need a large capacity fuse or fuse link in that circuit.

[Thipdar]

Is there a 1970 master wiring schematic posted somewhere that shows the 4 gauge instrument panel?

I think that the 1970 F350 master wiring diagram will be about as close as you can get.

[Thipdar]

Just got my alternator but it came with a serpentine pulley. There are several v-belt pulleys available, each with a different back spacing.

Does anyone know the correct back spacing on the stock 64 amp alternator?

Thanks

If it has a serpentine pulley, it's not the right alternator for your truck.

Return it and tell them to get you the right alternator - and the right pulley - for your year of truck. If you need to, show them a picture of the alternator and pulley. It may be that they can swap the pulley from your old unit to a new unit (I've had that happen at the parts dealer before), but still... if you're paying your money, get the right thing!

[jingo]

FWIW after the fact, the 100A single wire installation works just fine. The old voltage regulator block sits disconnected, with just three, new heavier cables needed - battery, alternator, and starter. And a new matching ground wire. I get a constant 14.4V, 100A instead of 65A, & everything works great. I don't now why anyone would mess around with an old, unregulated alternator. Seems like trying to save a little dough in a part of the build where the risk/reward is low.

[DisneysPatB]

A full write up on the steps you took would probably be beneficial to others.

[bluef250]

There is a lot of information on changing alternators on the net.

One-wire alternators do not start generating power until a certain rpm and need a resistor/light to begin powering up at low speeds.

3G's can be swapped and successfully. Here is a link.

http://fordification.com/forum/viewtopi ... =8&t=13062

[Busboy]

I prefer keeping things original. However my 71 came with a transistorized voltage regulator which complicates things significantly. It has a remote separate field relay, different wiring harness etc. There is no replacement available for the regulator so when I got the truck it had been cobbled with a conventional regulator and "additional" wiring. I spent all day studying a 70 wiring diagram since a 71 is not listed on this website. After remodifying the original harness and eliminating the additional field relay, it seems to charge ok, maybe a little high but that's not unusual for Fords.